The present invention relates to the art of medical imaging. It finds particular application in conjunction with computed tomography (CT), and will be described with particular reference thereto. However, it is to be appreciated that the present invention is also amenable to other like applications and imaging modalities, e.g., magnetic resonance imaging (MRI), single photon emission computed tomography (SPECT), positron emission tomography (PET), fluoroscopy, etc.
Various modalities and types of medical imaging have been found to be useful in the diagnosis of pathology and the planning of therapeutic treatments and surgeries. In particular, conventional modalities of medical imaging (e.g., CT, MRI, SPECT, PET, fluoroscopy, etc.) accord medical professionals the benefit of non-invasive visualization of the patient""s anatomy in order to diagnosis conditions and plan treatments.
In an oncological application, for example, medical images are often used to visualize, identify and locate a cancerous tumor. Once identified and located, a medical professional may therapeutically or surgically treat the tumor with guidance from the medical images. Radiotherapy, e.g., involves obliteration of the tumor by delivering an appropriate dose of targeted radiation to the tumor or cancerous tissue. The goal is to completely obliterate the tumor or cancerous tissue while minimizing the radiation received by and/or damage to the surrounding tissue.
High precision image-guided radiotherapy systems have evolved to deliver the desired radiation dose to a desired volume or cross-section. The introduction of multi-leaf collimators (e.g., an 80-100 leaf collimator) on linear accelerators allows the delivery volume or cross-section to be highly spatially resolved. That is, in the planning of the therapy, the radiation delivery area or volume can be made to closely match the size and shape of the cancerous tumor to be obliterated.
While beneficial from the standpoint of accuracy in the radiation delivery, the high precision radiotherapy systems have exposed certain limitations in the medical imaging systems and techniques used to guide the radiotherapy. For example, to accurately and precisely visualize, identify and locate the pathology of interest for diagnosis and therapy planning, typically, a high spatial resolution image(s) of the region including the surrounding anatomy is obtained at high speed. Often, this imaging is carried out some time prior to administering the therapy or treatment. The obtained image(s) generally represents a xe2x80x9cstill picturexe2x80x9d of the patient""s anatomy at a particular instant in time, i.e., when the image was obtained.
Unfortunately, at the time of treatment (as opposed to the time of imaging), the tumor to be obliterated, e.g., may have shifted relative to the surrounding anatomy or other reference points. Moreover, administration of the therapy or treatment is not typically instantaneous. That is, the delivery of the targeted radiation, e.g., occurs over time. The treatment or delivery time can be anywhere from 5 to 30 minutes. During this time, the cancerous tumor may be moving relative to the surrounding anatomy or other reference points due to natural biological functions or cycles such as, e.g., respiration, cardiac function, etc. As the tumor moves about, portions thereof will enter and leave the targeted area or volume into which the radiation is being delivered. Accordingly, parts of the tumor may receive less than the planned dose of radiation thereby confounding complete obliteration of the tumor. Additionally, surrounding tissue may be pulled or pushed or otherwise moved by the biological function into the target area or volume and undesirably irradiated and/or damaged.
The present invention contemplates a new and improved planning target volume (PTV) and related technique which overcomes the above-referenced problems and others.
In accordance with one aspect of the present invention, a method of medical imaging is provided. The method includes obtaining at a first temporal resolution a first medical image of a region of interest of a patient, and obtaining at a second temporal resolution a second medical image of the region of interest. The second temporal resolution is lower than the first temporal resolution. The method also includes registering the first and second medical images with one another such that common reference points in the first and second medical images coincide. Finally, the first and second medical images are superimposed over one another.
In accordance with another aspect of the present invention, a medical imaging apparatus includes a medical imager which produces image representations of a region of interest of a patient at two different temporal resolutions. Registration means align with one another first and second image representations of the same region of interest obtained from the medical imager at different first and second temporal resolutions, respectively. Combining means then superimpose over one another the aligned first and second image representations.
One advantage of the present invention is the ability to visualize, for a targeted tissue mass or tumor, a range or envelope of motion experienced due to normal biological functions.
Another advantage of the present invention is the ability to accurately and precisely visualize the size and/or shape of a targeted tissue mass or tumor.
Yet another advantage of the present invention is relatively improved and flexible treatment planning as compared to previously developed systems and/or techniques.
Still further advantages and benefits of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description of the preferred embodiments.